It’s a known fact that plants require nutrients for growth and the more organic you go, the better it is for them. Even for us humans, too much food causes problems, but when taken in good amounts, it keeps you healthy. For the plants, the fact is similar too.

Overusing compost will definitely hurt your plant. Compost contains nitrogen, phosphorus, potassium, and carbon. Although plants do require them for their growth, but too much of these elements do damage root system and plants a lot.

To understand how overusing of compost affects plants, we should know what compost is, its ingredients and how it affects plants.

What is Compost?

Compost is decomposed organic material. When organic material like vegetables, stems, and animal products get decomposed by micro-organisms in the environment.

Plants, as they grow with time, absorb all the required nutrients from the soil, making the soil infertile and useless for further growth of the plant. Adding compost revitalizes the soil and makes it nutrient-rich so that plants can get all the nutrients and focus on its growth.

No wonder compost does its magic, but we should know that the nutrient value of compost depends on the material which is decomposed to create it.

Suppose, if you decompose something high in nitrogen, your compost will contain a lot of nitrogen and you’ll have to use it in the right amount so you don’t intoxicate the soil with excess nitrogen.

Compost to Soil Ratio

The first thing you should do is know the composition of th compost and soil. There are kits available in the market which you can use to know the ratio of different minirals in the soil. However, not everyone want’s to do it.

You can use 20-50% of compost in your potting mix depending on the quality of the compost.

Problems with Phosphorus levels in Compost

Phosphorus takes a lot of time in getting depleated. And when you keep adding compost into the same soil, you’re adding more phosphorus into same soil. This isn’t a problem in the beginning but in long time, there will be a lot of phosphorus in soil and it will stop the growth of the plants and cause other problems.

A suggestion is to change the soil of the plant in every 16-18 months so that you never have to deal with that problem.

Effects of too much compost in soil

Root Burn

When compost is very fresh or concentrated, they’re very high in nutrients and plants usually don’t require too much of anything. If your compost is having very high amount of minirals, it will burn the roots and if not treated properly, the plant may even die.

Nutrient Imbalance

If you add too much compost, your potting mix will have minirals which were in compost in higher quantity which will create a nutrient imbalance and then plants will show different symptoms depending on excess and deficiency of different minirals

Soil pH

The materials which are decomposed for creating compost decide the pH of the compost. Too much of compost can make the soil either very acidic or basic and if you’re plant isn’t happy about that environment, it will harm the plant.


Adding too much compost can also lead to soil compaction. This happens because compost tends to be fluffy and becomes densely packed when added in large amount. Compacted soil can make it difficult for roots to grow and absorb nutrients.

Water Retention

While compost is beneficial for the soil structure. But too much of compost can make the potting mix water logged which is the main reason behind root rot.

Microbial Imbalance

Compost is full of microganisms which do benefit plants in some quantities, if there is too much compost, it can create imbalance in the microorganisms from compost and microorganisms from the soil which are required for good growth of plants.

Ways of Adding Compost into Soil

Mix it with the soil/potting mix

You can always mix the compost in the soil while you’re potting the plant. But before you do that make sure that the compost you’re using is fully decomposed and is not very fresh.

How much compost to mix with the potting mix?

Although some people will tell you to use 50% compost. But don’t do it if you don’t know too much about your compost. Do not use more than 35% compost in the mix.

Top Dressing of the Soil with Compost

If you are skeptical about mixing the compost into the soil, the best way is to add a layer of compost on the top layer of the plant. Every time you water it, the nutrients will get absorbed into the soil and will. reach the plant slowly and effectively.

Top dressing is something that you should do almost once in every two-three months for proper growth of plants.

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